Study of the K − → e − νπ 0 decay

Abstract

The decay K − → µ − νπ 0 has been studied using in-flight decays detected with "ISTRA+" setup operating in the 25 GeV negative secondary beam of the U-70 PS. About 112K events were used for the analysis. The λ + and λ 0 slope parameters of the decay formfactors f + (t), f 0 (t) have been measured : λ + = 0.0321 ± 0.004(stat) ±0.002(syst) λ 0 = 0.0209 ± 0.004(stat) ±0.002(syst); the correlation dλ 0 /dλ + = −0.46 The limits on the possible tensor and scalar couplings have been derived: f T /f + (0) = −0.021 ± 0.028(stat) ±0.014(theory); f S /f + (0) = 0.004 ± 0.005(stat) ±0.005(theory)

Spin alignment of mesons produced in neutron-carbon interactions

“…An early experiment [2] reported no spin alignment of K * (892) ± produced in pp interactions at 12 and 24 GeV. Significant spin alignment has been observed for leading vector mesons inclusively produced by charged kaons: for K * (892) + and K * (892) 0 in K + p reaction at 8.2 GeV [3], 32 GeV [4] and 70 GeV [5], for K * (892) − and K * (892) 0 in K − p interactions at 14.3 GeV [6] and 32 GeV [7].…”

Experimental study of direct photon emission in K/it− → π−π0γ decay using ISTRA+ detector

“…The experiment has been performed at the IHEP proton synchrotron U-70 with the experimental apparatus ISTRA+, which is a modification of the ISTRA-M setup [14] and which was described in some details in our recent papers where studies of the K − e3 [15], K − µ3 [16] and K − π3 [17] decays were presented. The setup is located in the negative unseparated secondary beam with the following parameters during the measurement: the momentum is ∼ 25 GeV/c with σ(p)/p ∼ 1.5 %, the admixture of kaons is ∼ 3 %, and the total intensity is ∼ 3×10 6 per spill.…”

“…The trigger is provided by the scintillation counters S1-S5, the Cherenkov counterš C0-Č2 and the analog sum of the amplitudes from the last dinodes of the calorimeter SP1 (see Refs. [15,16] for details). The latter serves to suppress the dominating K − → µ −ν µ decay.…”

“…The details of the reconstruction procedure have been published in Refs. [15,16], here only key points relevant to the K − → π − π 0 γ event selection are described.…”

“…To suppress leptonic K − decays the particle identification is used. The electrons are identified using the ratio of the energy of the shower, detected in the calorimeter SP1 and associated with the track of the electron, to the momentum of the electron [15]. The muons are identified using the information from the calorimeters SP1 and HC [16].…”